An integrating sphere is a well known device for providing a uniform light source and essentially comprises a spherical cavity with two ports and whose inner surface is coated with uniform, diffusely reflecting, white paint. One port allows light to enter the cavity, the other allows light to exit the cavity and be observed by a light detector. In many applications involving an integrating sphere, it is of interest to place a sample inside the cavity so that the light coming through the entrance port can strike it causing it to emit light which is then collected and observed. By producing multiple internal diffuse reflections, the integrating sphere provides uniform irradiation of the exit port irrespective of the direction in which light is emitted from the sample. A light detector placed at the exit port, therefore, sees a uniform spectral radiance that is proportional to the spectral flux emitted from the sample.